Edge detection device, an edge detection method, and an object holding device

ABSTRACT

According to one embodiment, an edge detection device includes a light source, an imaging part, and a detector. The light source includes at least three light-emitting parts for irradiating a plurality of objects adjacent with a light. The imaging part images a surface of the objects irradiated by each of the light-emitting parts, and generates a plurality of image data of the surface. The detector detects edges of the surface imaged, based on at least two different combinations of the plurality of image data.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-200197, filed on Oct. 11, 2016, andJapanese Patent Application No. 2017-162757, filed on Aug. 25, 2017; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an edge detectiondevice, an edge detection method, and an object holding device.

BACKGROUND

Presently, in distribution and logistics industry, by spread ofmail-order market, the handling amount of objects has tendency toincrease. As a result, each logistics company copes with automation ofthe logistics system.

As to conveyance and safekeeping of objects in warehouse, automationusing belt-conveyer is progressed. However, as to transfer working (suchas depalletizing and picking) to move objects to another place,automation is difficult, and an idea to automate is necessary. In orderto automate the transfer working, correctly-detection of loading statusand location status of objects is very important. As the detectionmethod, by irradiating from each of a plurality of light sources toobjects, and by imaging a reflected light from the objects bytwo-dimensional image sensor (and so on), edges and boundaries of theobjects are detected from the image. In this method, for example, if aplurality of objects is adjacent and located three-dimensionally, edgesand boundaries thereof cannot be correctly detected. Accordingly, evenif the plurality of objects is adjacently located, a device able tocorrectly detect edges and boundaries thereof is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view showing one example of an edge detection device 1according to the first embodiment.

FIG. 2 is an enlarged view showing one example of imaging parts andedges of two objects on condition that lights are irradiated fromdifferent positions.

FIG. 3 is a flow chart of edge detection processing by a detectoraccording to the first embodiment.

FIG. 4 is image data showing one example of location of a plurality ofboxes (objects).

FIG. 5 is a schematic diagram showing location of light sources and theimaging part used for the first embodiment.

FIG. 6 is two image data acquired by irradiating from different lightsources, and two difference images between respective image data.

FIG. 7 is image data acquired by multiplying the two difference images.

FIG. 8 is a top view showing one example of the edge detection device 1according to the second embodiment.

FIG. 9 is a top view showing one example of the edge detection device 1according to the third embodiment.

FIGS. 10A and 10B are a top view and a front view showing one example ofan object holding device according to the fourth embodiment.

FIG. 11 is a schematic diagram showing one example of objects eachhaving an appendix on surface thereof.

FIG. 12 is a schematic diagram showing one example of objects bundled byan appendix.

FIGS. 13A and 13B are a regular color image acquired by imaging objects,and an edge detection image acquired by the edge detection device of thethird embodiment.

FIG. 14 is one example of a plurality of images of which color isdivided by saturation.

FIGS. 15A and 15B are a regular color image acquired by imaging objects,and an image acquired by overlapping an external shape of each ofcolor-divided image data.

FIG. 16 is a flow chart of processing of edge detection method accordingto the fifth embodiment.

DETAILED DESCRIPTION

According to one embodiment, an edge detection device includes a lightsource, an imaging part, and a detector. The light source includes atleast three light-emitting parts for irradiating a plurality of objectsadjacent with a light. The imaging part images a surface of the objectsirradiated by each of the light-emitting parts, and generates aplurality of image data of the surface. The detector detects edges ofthe surface imaged, based on at least two different combinations of theplurality of image data.

Hereinafter, an edge detection device according to embodiments aredescribed below with reference to drawings. Having the same referencenumeral means the same component. Incidentally, the drawings areschematic or conceptual, a relationship between the thickness and widthof each part, the dimensional ratio between parts, etc. are notnecessarily the same as actual ones. Furthermore, even the same part maybe depicted in the different dimensions or dimensional ratio among thedrawings.

The First Embodiment

The first embodiment will be explained by referring to FIG. 1. FIG. 1 isa top view showing one example of the edge detection device 1 accordingto the first embodiment.

As shown in FIG. 1, a plurality of objects G is placed opposite to theedge detection device 1.

Here, in order to simplify explanation, +X-direction, −X-direction,+Y-direction, −Y-direction, +Z-direction, and −Z-direction will bedefined. For example, +X-direction, −X-direction, +Y-direction, and−Y-direction, are directions approximately parallel to a horizontalplane. −X-direction is a direction opposite to +X-direction. In thefirst embodiment, +X-direction is a direction along which the objects Gis positioned for the edge detection device 1. As shown in FIG. 1, thedirection along which the objects G is positioned for the edge detectiondevice 1 is a direction from the edge detection device 1 to the objectsG. +Y-direction is a direction crossing +X-direction (For example,approximately-perpendicular direction). −Y-direction is a directionopposite to +Y-direction. +Z-direction is a direction crossing+X-direction and +Y-direction (For example, approximately-perpendiculardirection), i.e., approximately-vertical upward direction. As shown inFIG. 1, +Z-direction is a direction along this side of the paper (FIG.1). −Z-direction is a direction opposite to +Z-direction, for example,approximately-vertical downward direction.

The plurality of objects G is adjacently located, for example, placed ona shelf. Alternatively, they may be placed on a pallet, a basketcarriage, or a box pallet. The objects G may be loaded in a pile.Furthermore, a shape of the object G is a cuboid or a cube. For example,it is a cardboard box or a container in which commodities are packed.The shape of the object G is not limited to the cuboid and so on. It maybe a polyhedron.

An edge of the object G is an edge portion or a boundary of face of theobject. The edge is not all of edge parts or boundaries of some face ofthe object, and includes a part thereof. Namely, if a shape of the faceis a rectangle, the edge may be any of an edge along a verticaldirection and an edge along a horizontal direction. Furthermore, among aplurality of faces forming the object, the edge includes a corner, aborder and an edge where two faces contact.

As shown in FIG. 1, the edge detection device 1 equips a light source 2,an imaging part 3, a detector 4, a controller 5, and a display 6. Thelight source 2 irradiates the plurality of objects G with a light. Theimaging part 3 images faces of the plurality of objects G (irradiated byeach light-emitting part 21˜24 of the light source 2), and acquires aplurality of image data as the imaging result. The detector 4 detectsedges of faces of the objects G imaged, based on the plurality of imagedata. The controller 5 controls driving of the light source 2 and theimaging part 3. The display 6 displays edge information of the objects G(detected by the detector 4).

The edge detection device 1 detects edges of face from image data of theface of the plurality of objects G (imaged). Here, the face is a faceamong the plurality of objects G, which is irradiated by the lightsource. The edge detection device 1 detects a part where brightnesssuddenly changes from the image data, and detects this part as an edgeof the object.

In the first embodiment, the light source 2 includes four light-emittingparts 21˜24. The light-emitting parts 21˜24 irradiate the plurality ofobjects G with a light, and each of the light-emitting parts 21˜24 islocated at different positions. The light-emitting parts 21˜24respectively irradiate at different timings, and irradiate the pluralityof objects G with a light.

As shown in FIG. 1, the light-emitting parts 21˜24 are located so as tobe opposing the objects G, and irradiate a region including a face B ofthe objects G with a light. The face B of the objects G is a face imagedby the imaging part 3 as a detection target of edges of the objects G.The region including the face B is not limited to the face B of theobjects G opposing the light source 2. The face B includes other faceand region of the objects (except for the face B) to be irradiated. Thelight-emitting parts 21˜24 are located so as to put a plane Dtherebetween. The plane D includes a line segment A (chain line)connecting the objects G with the imaging part 3, and is in parallel toa direction C of edges to be detected. The line segment connecting theobjects G with the imaging part 3 may be a line segment connecting oneof the objects G with the imaging part 3, or a line segment connecting acenter of a distance between one end and the other end of the objects G(aligned along Y-direction) with the imaging part 3. Furthermore, thelight source 2 may be located at the side along −X-direction than theimaging part 3. Namely, the line segment includes a line extending fromthe objects G through the imaging part 3.

The direction of edges to be detected is a direction of detectableedges, based on locations of the light-emitting parts 21˜24 (explainedafterwards). In the first embodiment, it corresponds to the direction Cof edges in FIG. 1. The plane D is a face including the line segment Aand in parallel to the direction C. “so as to put a plane Dtherebetween” means, the light-emitting parts are classified into twogroups (or two sets), and are located so as to put the plane D betweentwo classes. For example, in the case of four light-emitting parts asshown in FIG. 1, they are preferably classified by twos, and located soas to put the plane D therebetween. Furthermore, four-emitting parts maybe classified into one part and three parts, and located so as to putthe plane D therebetween. The light-emitting parts 21 and 23 are locatedat a region (it is called a first region) along +Y-direction for theplane D. The light-emitting part 21 is located near the objects G, andthe light-emitting part 23 is located at the side along −X-directionfrom the light-emitting part 21. On the other hand, the light-emittingparts 22 and 24 are located at a region (it is called a second region)along −Y-direction for the plane D. The light-emitting part 22 islocated near the objects G, and the light-emitting part 24 is located atthe side along −X-direction from the light-emitting part 22. The lightsource 2 (four light-emitting parts 21˜24) are preferably located at awidth wider than a width of the objects G along Y-direction. Forexample, in the case of viewing the objects G from −X-direction, twolight-emitting parts 21 and 23, and two light-emitting parts 22 and 24,are preferably located so as to put the plane D therebetween.

As shown in FIG. 1, the light-emitting parts 21˜24 respectivelyirradiate the objects G with a light. Accordingly, while onelight-emitting part is irradiating the objects G with a light, otherlight-emitting parts are located so as not to enter into an irradiatedregion of the one light-emitting part. Here, the irradiated region is aregion formed by a projection line where the objects G are perspectivelyprojected by one light-emitting part (viewpoint). In FIG. 1, a brokenline is the projection line of the light-emitting part 21, and ahutching part is the irradiated region.

Location of the light-emitting parts 21˜24 will be explained in detail.Here, for the plane D including the line segment A (connecting a centerof objects G aligned along Y-direction with the imaging part 3) and inparallel to the direction C of edges, two light-emitting parts 21 and23, and two light-emitting parts 22 and 24, are almost symmetricallylocated. First, by setting a location of the light-emitting part 21 to areference, the light-emitting part 23 is located at outside of theirradiated region (hutching part in FIG. 1) of the light-emitting part21. This reason is, if the light-emitting part 23 is located in theirradiated region, when the light-emitting part 23 irradiated theobjects G with a light, a shadow of the light-emitting part 21 isreflected onto the objects G, and the image data includes a falsesignal. The false signal is a signal except for desired signal, i.e., anoise component. Moreover, locations of other light-emitting parts 22and 24 are same as those of the light-emitting parts 21 and 23.Furthermore, a distance from the objects G to the light-emitting parts21 and 23 is preferably equal to a distance from the objects G to thelight-emitting parts 22 and 24. Furthermore, two light-emitting parts 21and 23, and two light-emitting parts 22 and 24, are not always symmetricto the plane D.

As the light-emitting parts 21˜24 of the light source 2, an incandescentlamp, a halogen lamp, a fluorescent light, a discharge lamp, e.g., LED(light emitting diode), can be used. However, the light-emitting parts21˜24 are not limited to them. Furthermore, a shape of the light source2 may be separated into a plurality of units, or formed as one body. Forexample, if the light source 2 is separated into four units (e.g., fourincandescent lamps are located), the four units may be respectively alight-emitting part. Furthermore, if the light source 2 is formed as onebody (e.g., LED board capable of lighting from each position thereof),four parts (each lighting differently) of the light source 2 may berespectively a light-emitting part. Furthermore, if the light source isseparated into two units (e.g., LED is located to be rod-like, and twoline lights (each having a predetermined part capable of lighting) arealigned), the respective predetermined part of two line lights may betwo light-emitting parts. In above explanation, the light source 2includes by four light-emitting parts 21˜24. However, the light source 2is not limited to this component. The light source 2 may include threelight-emitting parts or five (or more than five) light-emitting parts.Furthermore, in above explanation, the light source 2 is located on thesame plane as (or a plane in parallel to) a plane where the objects Gare place. However, the plane on which the light source 2 is not limitedto them.

The imaging part 3 images the plurality of objects G irradiated by eachlight-emitting part 21˜24, and acquires respective image data. The imagedata corresponds to the imaging result which the imaging part 3 imagesthe objects G and circumference thereof. For example, image datagenerally used such as RAW data, jpg, gif, png or bmp, may be applied.

As shown in FIG. 1, the imaging part 3 is located at the side (opposingthe objects G) where the light source 2 is positioned. Namely, theimaging part 3 is located along −X-direction for the objects G, andimages a face B of the objects G from −X-direction. The imaging part 3is preferably located at a position apart from a center of the objects G(aligned along Y-direction) toward −X-direction. The imaging part 3acquires image data when the light-emitting parts 21˜24 respectivelyirradiate the objects G. Specifically speaking, in the first embodiment,the number of light-emitting parts is four, and the number of image datais also four. Namely, the number of image data is equal to the number oflight-emitting parts, but not limited to this. The image data is imagesincluding at least face B of the objects G (opposing the imaging part3). The image data is stored in storage 3A of the imaging part 3. Forexample, as the storage 3A, a tape system such as a magnetic tape or acassette tape, a disk system such as a magnetic disk (floppy disk(registered trade mark)/hard disk) or an optical disk(CD-ROM/MO/MD/DVD/CD-R), a card system such as an IC card (including amemory card) or an optical card, and a semiconductor memory system suchas a mask ROM/EPROM/EEPROM/flash ROM, may be used. The imaging part 3may use a memory (to store the image data) installed at the outside.

The imaging part 3 includes an optical system such as a camera, a CCD(Charge Coupled Device) sensor, or an imaging element such as a CMOSsensor (Complementary Metal Oxide Semiconductor).

The imaging part 3 may include one camera. However, the imaging part 3is not limited to this component.

The detector 4 detects edges of the face B of the objects G, based on aplurality of image data imaged by the imaging part 3. The edges are aborder, an outline, or a boundary having uneven shape on the face B ofthe objects G. In the image data, a part where brightness suddenlychanges corresponds to the edges.

FIG. 2 is an enlarged view showing one example of imaging part 3 andedges of two objects on condition that the two objects are irradiatedfrom different positions. As shown in FIG. 2, a light from thelight-emitting part 21 at the right side is represented as solid lines,and a light from the light-emitting part 22 at the left side isrepresented as broken lines. In FIG. 2, lights scattered at a surface(including edges) of objects and toward the imaging part 3 are onlyshown. In general, edges of objects (such as a cardboard box) are not aperfect right angle and include a slope or roundness. If thelight-emitting part 21 irradiates the objects including such edges witha light, due to relationship of irradiation angle of the light, edges ofthe object located at the left side in FIG. 2 are shined by many lights,and these lights are scattered toward the imaging part 3. On the otherhand, edges of the object located at the right side in FIG. 2 are hardto be shined by many lights. In the same way, if the light-emitting part22 irradiates with a light, edges of the object located at the rightside in FIG. 2 are shined by many lights, but edges of the objectlocated at the left side in FIG. 2 are hard to be shined by many lights.If image data are acquired by irradiating from respective light-emittingparts located at right and left, two image data in which brightness ofedges are different (due to position of the light-emitting part) areacquired. By calculating a difference between these two image data, arelative large difference occurs at the edges. Accordingly, the edges ofthe objects can be detected. The difference between two image data isacquired by comparing each pixel (two corresponding pixels) between twoimage data and by remaining different pixels therebetween. The comparingeach pixel means, two corresponding pixels at the same pixel positionbetween two image data are compared. For example, in the differencebetween two image data, a pixel position having the same pixel valuetherebetween is displayed blackly, and a pixel position having differentpixel value therebetween is displayed whitely. Display with black andwhite may be reverse, or the pixel position may be displayed withanother color.

Next, in the first embodiment, a method for detecting edges of theobjects G by the detector 4 will be explained in detail.

In the first embodiment, the detector 4 detects edges of the objects Gfrom four image data of the objects G irradiated respectively by fourlight-emitting parts (located at different positions). In order tosimplify the explanation, while the light-emitting part 21 is lighting,an image acquired by the imaging part 3 is called image data 31 (notshown in Fig.). In the same way, while the light-emitting parts 22, 23and 24 are lighting respectively, images acquired by the imaging part 3are called image data 32, 33 and 34 (not shown in Fig.).

In addition to this, four image data 31˜34 are classified into a firstcombination and a second combination.

Here, as for the plane D including the line segment A (connecting theobjects G with the imaging part 3) and in parallel to the direction C ofedges, one is selected from two image data 31 and 33 (irradiated by twolight-emitting parts 21 and 23 located along +Y-direction), and one isselected from two image data 32 and 34 (irradiated by two light-emittingparts 22 and 24 located along −Y-direction). By combining the selectedone, the first combination and the second combination are generated. Forexample, the first combination is image data 31 and image data 32, andthe second combination is image data 33 and image data 34.

The reason for this combination is, if two image data acquired byimaging along the same direction are combined, as mentioned-above,difference does not occur at edges in the difference image. As a result,the edges of the objects G cannot be correctly detected.

Moreover, as the combination of image data, image data 31 and image data34 may be the first combination, and image data 32 and image data 33 maybe the second combination. Furthermore, by combining any of image data31 and image data 33 with image data 32 or image data 34, the firstcombination and the second combination may be generated. Furthermore, bycombining any of image data 32 and image data 34 with image data 31 orimage data 33, the first combination and the second combination may begenerated.

After generating the first combination and the second combination, inorder to detect edges from each combination, by calculating a differencebetween two image data included in the same combination, a differenceimages of each combination is generated. After that, in order to removea false signal, two pixel values at the same pixel position between twodifference images are multiplied for each pixel. In this way, edges ofthe objects G are detected.

Hereinafter, processing after generating the first combination and thesecond combination will be explained in detail.

First, before acquiring the difference image, correction processing isperformed to two image data (included in the same combination) so thatbrightness of low spatial frequency components of two image data isequal. For example, this processing is performed by following steps.

By averaging two image data (included in the same combination),reference image data is generated. Specifically, a sum of two pixelvalues (at the same pixel position) between two image data iscalculated, and the sum is divided by two (step 1). In order to extracta low spatial frequency component of two image data, filtering by lowpass filter is performed to each image data (step 2). The filtering bylow pass filter is removing a high spatial frequency component higherthan a predetermined spatial frequency component, e.g., a method usedfor blurring a fine pattern in the image. Furthermore, each of twoimages is divided by the filtered image data (generated at step 2) foreach pixel. As to each image data divided, the reference image data(generated at step 1) is multiplied for each pixel position (step 3).The division of image data is processing to emphasize a different partand blur the same part in the image data. Furthermore, themultiplication of image data is processing to emphasize the same partand blur a different part in the image data.

As the reason for such correction of brightness, a noise component dueto difference of brightness between two image data is remained indifference processing (explained afterwards). Accordingly, remaining ofthe noise component needs to be avoided. Moreover, a signal of edge tobe detected represents a characteristic at high spatial frequencycomponent. Accordingly, correction processing is performed to lowspatial frequency component only.

Next, processing to emphasize edges of image data is performed to eachimage data. This reason is, as an edge adjacent part of the object, onlypart where change of brightness is relatively large needs be extracted.In this processing, for example, filtering is performed by a high passfilter such as Prewit filter, Sobel filter, or Roberts filter. Thefiltering by high pass filter is removing a low spatial frequencycomponent lower than a predetermined spatial frequency. e.g., a methodused for emphasizing a fine pattern in the image.

After performing above processing to two image data, a differencebetween two image data is calculated, and an absolute value of thedifference is calculated. This series of processing is performed to thefirst combination and the second combination. As a result, image datahaving a characteristic at edge part is acquired for each combination.Here, in respective image data of the first combination and the secondcombination after above processing, a false signal (such as a boundaryof shadow due to adjacent object, a reflected light) except for edge isalso detected. This false signal is more notable in the case that alevel difference exists at a face of the objects G (adjacently located)toward the side of the light source 2. Namely, in the case that a shapeor a size of the objects G are not equal, or even if the shape and thesize are equal, the objects G are aligned by shifting along X-direction,the false signal occurs. This false signal is not discriminated fromedges, and erroneously detected as the edges. Accordingly, in order toreduce the false signal, two image data (acquired by above processing)are multiplied for each pixel position. As a result, the false signalcomponent (such as a shadow due to adjacent objects, or a reflectedlight) can be reduced. In this processing, the fact that “a boundary ofshadow due to adjacent objects, and a position where the reflected lightoccurs, is changed by a position of the light source 22” is utilized.Namely, a position of the false signal in image data acquired from thefirst combination is different from a position of the false signal inimage data acquired from the second combination. Contrary to this, edgesto be detected exist at the same position in respective image dataacquired from the first combination and the second combination.Accordingly, by multiplying two image data (after above processing) foreach pixel position, the edge signal is larger while the false signal issmaller.

As following processing, if necessary, elimination processing ofisolated points (it is called Morphology operation) and thickeningprocessing may be added. Furthermore, after that, binarizationprocessing may be added. The binarization processing is processing toconvert the image into two gradations (black and white). By setting athreshold, if a value of a pixel is above the threshold, the value ofthe pixel is replaced with a white pixel. If a value of a pixel is belowthe threshold, the value of the pixel is replaced with a black pixel.

In the edge detection device of the first embodiment, the light-emittingparts are located on the same plane where the objects G are placed.Accordingly, among edges of the objects G, an edge aligned along adirection perpendicular to the plane (where the light-emitting parts arelocated) can be notably detected. Namely, an edge aligned alongZ-direction of the objects G can be detected. This means, a direction ofnotably-detectable edges is determined due to location of thelight-emitting parts.

FIG. 3 is a flow chart of above-mentioned edge detection processing bythe detector 4 according to the first embodiment.

First, the detector 4 acquires four image data from the storage 3A(S301). The detector 4 classifies the four image data into a firstcombination and a second combination (S302).

The first combination is two image data 31 and 32. The secondcombination is two image data 33 and 34.

As to two image data 31 and 32 of the first combination, correctionprocessing is performed so that brightness of a low spatial frequencycomponent thereof is equal (S303). As to two image data 31 and 32, edgeemphasis processing is performed (S304). As to two image data 31 and 32,a difference therebetween is calculated, and a first difference imagedata is acquired (S305). As to the first difference image data, absolutevalue processing is performed (S306).

On the other hand, as to two image data 33 and 34 of the secondcombination, correction processing is performed so that brightness of alow spatial frequency component thereof is equal (S307). As to two imagedata 33 and 34, edge emphasis processing is performed (S308). As to twoimage data 33 and 34, a difference therebetween is calculated, and asecond difference image data is acquired (S309). As to the seconddifference image data, absolute value processing is performed (S310).

Next, as to the first difference image data and the second differenceimage data, multiplication processing is performed for each pixelposition (S311). As to the multiplied image data, elimination processingof isolated points and thickening processing are performed (S312). As tothe acquired image data, binarization processing is performed (S313). Inthis way, in the objects G, edges at the face toward the light source 2and the imaging part 3 are detected.

The multiplied image data is image data on which the false signal isblurred and only edges are emphasized.

For example, the detector 4 is packaged into a computer (equipping aprocessor and a memory) or LSI (large scale integration).

The controller 5 controls driving of the light source 2 and the imagingpart 3. The driving is On/Off operation of each of four light-emittingparts 21˜24 of the light source 2, and imaging operation of the imagingpart 3. In order to image the objects G irradiated by eachlight-emitting part, the imaging part 3 operates based on On/Off of thelight-emitting part. For example, on condition that only the lightemitting-part 21 is “On” to irradiate the objects G with a light, theimaging part 3 is operated to image the objects G. Next, on conditionthat the light-emitting part 21 is “Off” and only the lightemitting-part 22 is “On” to irradiate the objects G with a light, theimaging part 3 is operated to image the objects G. This operation isrepeated for other light-emitting parts 23 and 24. The order ofirradiation of the light-emitting parts 21˜24 is not limited to this.The light-emitting parts 21˜24 may irradiate in any order.

The controller 5 is a driver or a driver circuit to control operation ofthe light source 2 and the imaging part 3. The controller 5 can bepackaged into a computer 8 (equipping a processor and a memory) or LSI.Furthermore, the controller 5 may be included in the detector 4.

The display 6 displays edge information (detected by the detector 4) ofthe face of the objects G opposing the light soured 2 and the imagingpart 3. The edge information is image data including edges detected bythe detector 4, or information which the image data is visuallyrecognizable. As the display 6, a monitor of the computer, or an LCDmonitor of a portable terminal, may be used. The display 6 is notnecessary component for the edge detection device 1. The edge detectiondevice 6 may not include the display 6.

Next, practical examples of the edge detection device according to thefirst embodiment will be explained by referring to FIGS. 4˜7. As objectsbeing an edge detection target, eight boxes are adjacently aligned in alateral direction.

FIG. 4 shows an image in the case that a plurality of boxes (objects) islocated by adding a level difference (gradually larger from left toright) to each box along a depth direction. As shown in FIG. 4, thelevel direction between adjacent two boxes is, from left, 0 mm, 5 mm, 10mm, 20 mm, 30 mm, 40 mm, 50 mm.

FIG. 5 is a schematic diagram showing location of light sources and theimaging part used for the first embodiment. As shown in FIG. 5, theimaging part 3 is located opposing the plurality of boxes along−X-direction. As the light source, four light-emitting parts 21˜24 areused. Each light-emitting part is a line light-emitting part extendingalong Z-direction. As a distance from the boxes to the linelight-emitting part, two light-emitting parts 21 and 22 are located at aposition having 30 cm from the box along −X-direction. Furthermore, twolight-emitting parts 23 and 24 are located at a position having 100 cmfrom the box along −X-direction. The light-emitting parts 21 and 22, andthe light-emitting parts 23 and 24, are respectively located at aninterval 140 cm. As to a plane D including a line segment A connecting acenter of the boxes (aligned along Y-direction) with the imaging part 3,and in parallel to a direction C of edges to be detected, twolight-emitting parts 21 and 23, and two light-emitting parts 22 and 24,are symmetrically located.

FIG. 6 is two image data acquired by irradiating from the light-emittingparts 21 and 23, a difference between two image data acquired byirradiating from the light-emitting parts 21 and 22, and a differencebetween two image data acquired by irradiating from the light-emittingparts 23 and 24.

As shown in FIG. 6, in two image data acquired by irradiating from thelight-emitting parts 21 and 23, a shadow of adjacent two boxes is imagedat a position where the two boxes are located with a level difference. Aboundary of this shadow is detected from the difference image of theimage data, and this boundary cannot be discriminated from edges to bedetected. As a noteworthy fact, in the difference image in the case ofdistance 30 cm from the box to the light-emitting parts 21 and 22, andin the difference image in the case of distance 100 cm from the box tothe light-emitting parts 23 and 24, respective positions of the boundaryof the shadow are different.

FIG. 7 is image data acquired by multiplying the difference image(between two image data acquired by irradiating from the light-emittingparts 21 and 22) with the difference image (between two image dataacquired by irradiating from the light-emitting parts 23 and 24).

By multiplying two difference images, false signals (due to the boundaryof shadow) occurred at different positions are reduced, and edge signalsare correctly acquired.

By the edge detection device of the first embodiment, influence of thefalse signal such as a shadow or a reflected light (occurred by adjacentobjects) is reduced, and edges of the objects are correctly detected.

Furthermore, location of light-emitting parts 21˜24 of the edgedetection device 1 includes the case that at least one of thelight-emitting parts is offset along X-direction or Y-direction, isincluded. In this case, the same effect is acquired.

In above explanation, as to the plane D including the line segment Aconnecting a center of the objects G with the imaging part 3 and inparallel to the direction C of edges to be detected, four light-emittingparts are located along +Y-direction and −Y-direction by twos. However,one (light-emitting part 21) may be located along +Y-direction, andthree (light-emitting parts 22˜24) may be located along −Y-direction. Inthis case, while the light-emitting part 21 is lighting, an imageacquired by the imaging part 3 is image data 31. In the same way, whilethe light-emitting parts 22, 23 and 24 are lighting differently, imagesacquired by the imaging part 3 are image data 32, 33 and 34. Here, twoimage data 31 and 32 may be the first combination. Two image data 31 and33, or two image data 31 and 34, may be the second combination.Furthermore, two image data 31 and 33 may be the first combination, andtwo image data 31 and 34, may be the second combination. Furthermore,three (light-emitting parts 21, 23, 24) may be located along+Y-direction, and one (light-emitting part 22) may be located along−Y-direction. In this case, the first combination and the secondcombination are same as above-mentioned combinations.

In above explanation, combination of two image data is the firstcombination and/or the second combination. However, the number of imagedata to be combined is not limited to two. Combination of three imagedata (or image data more than three) may be the first combination and/orthe second combination.

Furthermore, in above explanation, from image data of objects irradiatedrespectively by the light-emitting parts (located at differentpositions), the first combination and the second combination areselected. However, the number of combinations is not limited to two, andmay be plural number larger than two. Among a plurality of combinations,a difference image between two image data by twos is calculated, andmultiplication processing is performed to two difference images. In thiscase, edges of objects can be detected.

The Second Embodiment

The second embodiment will be explained by referring to FIG. 8. FIG. 8is a top view showing one example of the edge detection device 1according to the second embodiment.

As shown in FIG. 8, in the edge detection device 1, the light source 2includes three light-emitting parts 21˜23. Other components are same asthose of the edge detection device 1 of the first embodiment.

The light-emitting parts 21˜23 are located on the same plane as (or aplane in parallel to) a plane where a plurality of objects G is placed.The imaging part 3 is located so as to be opposing the objects G along−X-direction. As to a plane D including a line segment A connecting theobjects G with the imaging part 3 and in parallel to a direction C ofedges to be detected, two light-emitting parts 21 and 23 are located ata side along +Y-direction, and one light-emitting part 22 is located ata side along −Y-direction. Location of the light-emitting parts 21˜23 isnot limited to this location. As to the plane D, two light-emittingparts 21 and 23 may be located at the side along −Y-direction, and onelight-emitting part 22 may be located at the side along +Y-direction.

The imaging part 3 is preferably located so that a distance to thelight-emitting part 22 therefrom is shorter than a distance to thelight-emitting parts 21 and 23 therefrom. As a result, it is avoidedthat a reflected light by the light-emitting part 22 is directly imagedby the imaging part 3. Accordingly, even if one light-emitting part 22is located at the side along −Y-direction, a false signal due to thereflected light can be reduced. If the imaging part 3 is located so asnot to occur the reflected light by the light-emitting part 22, areflected light by the light-emitting part located at the side along+Y-direction is often imaged by the imaging part 3. Accordingly, twolight-emitting parts 21 and 23 are located at the side along+Y-direction.

While the light-emitting part 21 is lighting, an image acquired by theimaging part 3 is image data 31 (not shown in FIG. 8). In the same way,while the light-emitting part 22 and 23 are lighting, respective imagesacquired by the imaging part 3 are image data 32 and 33 (not shown inFIG. 8).

Among three image data 31˜33, the detector 4 selects a first combinationhaving two image data 31 and 32, and a second combination having twoimage data 32 and 33. Following processing to detect edges is same asthat of the first embodiment.

Three light-emitting parts 21˜23 may not be controlled to light in orderand to image the objects G irradiated by each light-emitting part. Forexample, if three light-emitting parts irradiate with respective lightshaving different wavelengths (red, green, blue), by using color imagesensors (red, green, blue), the objects G can be imaged on conditionthat three light-emitting parts simultaneously irradiate with a light.The wavelength of light is preferably within a range larger than (orequal to) 400 nm and smaller than (or equal to) 2000 nm for eachlight-emitting part. Furthermore, desirably, the wavelength is largerthan (or equal to) 400 nm and smaller than (or equal to) 780 nm.

In the edge detection device 1 of the second embodiment, by reducing thenumber of light emitting parts to three, cost-down due to reduction ofthe number of parts, and reduction of processing time to detect edges,can be planned.

In above explanation, the number of light-emitting parts is three.However, the number of light-emitting parts may be one or two. In thiscase, by preparing a moving mechanism for the light-emitting part, thesame effect as the case of three or four light-emitting parts can beacquired. For example, if the source light 2 includes two light-emittingparts 21 and 22, one of two light-emitting parts 21 and 22 is moved to aposition where the light-emitting part 23 is located in the secondembodiment. As the moving mechanism, the light-emitting part may bemoved by equipping wheels or by using a rail (previously installed).Furthermore, by using a linear motion mechanism of an electric sliderloading a stepping motor, the light-emitting part may be moved.Furthermore, an electric cylinder may be used instead of the electricslider. After moving, by acquiring image data of the objects irradiatedby the imaging part 3, the same image data as the case of irradiating bythe light-emitting part 23 can be acquired. Moving of the light-emittingpart is controlled by the controller 5 and so on. In the case of onelight-emitting part, by moving this light-emitting part in the same way,the case of three or four light-emitting parts can be substitutedtherewith.

The Third Embodiment

The third embodiment will be explained by referring to FIG. 9. FIG. 9shows one example of the edge detection device 1 according to the thirdembodiment.

As shown in FIG. 9, in the edge detection device 1, the light source 2includes four light-emitting parts 21˜24. The light source 2 is locatedon a plane approximately perpendicular to the line segment A (connectingthe objects G with the imaging part 3). Other components are same asthose of the edge detection device 1 of the first embodiment.

In FIG. 9, the light-emitting parts 21˜24 are located on a planeapproximately in parallel to YZ-plane with a predetermined distancealong −X-direction from a plurality of objects G. Namely, thelight-emitting parts 21˜24 are located on a plane approximately inparallel to a face B (of the objects G) toward the side of the lightsource 2. The imaging part 3 is located to be opposing the objects Galong −X-direction. As to a plane D1 including a line segment A(connecting the objects G with the imaging part 3) and in parallel to adirection C1 of edges to be detected, the light-emitting parts 21˜24 arelocated so as to put the plane D1 therebetween. In this case, thedirection C1 is Z-direction. As to the plane D1, two light-emittingparts 21 and 23 are located at the side along +Y-direction, and twolight-emitting parts 22 and 24 are located at the side along−Y-direction.

Furthermore, in the case of location of the light-emitting partsaccording to the third embodiment, edges along Y-direction can bedetected. As to a plane D2 including a line segment A (connecting theobjects G with the imaging part 3) and in parallel to a direction C2 ofedges to be detected, the light-emitting parts 21˜24 are located so asto put the plane D2 therebetween. Namely, as to the plane D2, twolight-emitting parts 21 and 22 are located at the side along+Z-direction, and two light-emitting parts 23 and 24 are located at theside along −Z-direction. Preferably, distances from the plane D1 (or theplane D2) to each light-emitting part are approximately equal. Because,if possible, brightness (illuminance) by which each light-emitting partirradiates the objects G are desirably equal.

While the light-emitting part 21 is lighting, an image acquired by theimaging part 3 is image data 31 (not shown in FIG. 9). In the same way,while the light-emitting part 22, 23 and 24 are lighting, respectiveimages acquired by the imaging part 3 are image data 32, 33 and 34 (notshown in FIG. 9).

In the third embodiment, the detector 4 selects a first combinationhaving two image data 31 and 34, and a second combination having twoimage data 32 and 33. Among location of the light-emitting parts 21˜24,by combining respective image data acquired by irradiating from twolight-emitting parts located along a diagonal direction, edges alongY-direction (lateral direction) and Z-direction (vertical direction) ofthe objects G can be detected. Following processing to detect edgesusing the first combination and the second combination is same as thatof the edge detection device of the first embodiment.

Moreover, if two image data 31 and 33 are selected as the firstcombination, and if two image data 32 and 34 are selected as the secondcombination, edges of the objects G along Y-direction can be effectivelydetected. Furthermore, if two image data 31 and 32 are selected as thefirst combination, and if two image data 33 and 34 are selected as thesecond combination, edges of the objects G along Z-direction can beeffectively detected.

The light-emitting parts 21˜24 are preferably located at outside than aregion where the objects G are positioned, from −X-direction to view theobjects G. Here, the region where the objects G are positioned is aregion that the objects G are projected onto each place where thelight-emitting parts 21˜24 are positioned.

The light-emitting parts 21˜24 are preferably located at a regionbetween the objects G and the imaging part 3. However, locations of thelight-emitting parts 21˜24 are not limited to this location. Thelight-emitting parts 21′24 may be located at a position far from theimaging part 3 along −X-direction. Namely, locations thereof may besuitably changed based on usage environment.

In above explanation, the light-emitting parts 21˜24 are located on aplane approximately in parallel to YZ-plane. However, locations thereofare not limited to this plane. At least one of the light-emitting parts21˜24 may be offset along X-direction. Furthermore, at least one of thelight-emitting parts 21˜24 may be offset along Y-direction orZ-direction.

In above explanation, the number of light-emitting parts is four.However, the number of light-emitting parts may be at least three.

In the edge detection device 1 of the third embodiment, by locating thelight-emitting parts on a plane in parallel to a face of the objects Gto be imaged by the imaging part, edges along all (XYZ) directions canbe detected depending on combinations of the image data.

Furthermore, in the edge detection device 1 of the third embodiment,edges along a predetermined direction can be detected.

Furthermore, in the edge detection device 1 of the third embodiment, bylocating the light-emitting parts along a vertical direction(Z-direction), compact device design can be realized without uselessspace.

The Fourth Embodiment

The fourth embodiment will be explained by referring to FIGS. 10A and10B. FIGS. 10A and 10B are a top view and a front view showing oneexample of an object holding device 10 according to the fourthembodiment. The object holding device 10 equips the edge detectiondevice according to the first, second and third embodiments.

First, the object holding device 10 and circumference component thereofwill be explained. As shown in FIGS. 10A and 10B, a plurality of objectsG is loaded on a loading region 20. The object holding device 10 and aconveyance region 30 are fixed onto a ground. The object holding device10 selectively picks the objects G from the loading region 20, andtransfers the picked object to the conveyance region 30. The objectholding device 10 may be movable. For example, the object holding device10 can equip a roller (and so on) at a bottom thereof. Alternatively,the object holding device 10 can move along a rail.

The loading region 20 may be a pallet, a basket carriage, a box palletor a shelf to load the objects G. The loading region 20 may be movableby equipping a roller at the bottom, or may be fixed.

The conveyance region 30 conveys the objects G transferred by the objectholding device 10. For example, the conveyance 30 may be a beltconveyer, a carriage, a pallet, a workbench, or a cargo bed.

As shown in FIGS. 10A and 10B, the object holding device 10 includes aholding part 50, a driving part 60, a recognition part 70, and acontroller 80. The holding part 50 holds objects (to be transferred fromthe loading region 20 to the conveyance region 30), and moves theobjects being held thereby. The driving part 60 drives the holding part50. The recognition part 70 recognizes a shape of the object (existingon the loading region 20) from an image of the object. The controller 80controls operation of the holding part 50 by driving the driving part60.

The holding part 50 is connected to the driving part 60, and movablealong three axes directions. Specifically, the driving part 60 drivesthe holding part 50 along a vertical direction, a front-back directionand a lateral direction. As shown in FIGS. 10A and 10, an orthogonalcoordinate axes is set. Z-axis corresponds to the vertical direction,X-axis corresponds to the front-back direction, and Y-axis correspondsto the lateral direction. The front-back direction and the lateraldirection are in parallel to a horizontal direction, i.e., a plane wherethe object holding part 10 is installed. The horizontal direction is inparallel to a bottom of the object as a holding target. The holding part50 is installed so as to be opposing a top surface of the objects Gloaded on the loading region 20. For example, the holding part 50 equipsa plurality of suckers 51 connected to a vacuum pump (not shown in FIGS.10a and 10B), and holds the objects G by suction. The suckers 51 areinstalled on a back surface of the holding part 50.

Specifically, the driving part 60 equips support parts 61, 62 and 63. Asupport part 61 drives the holding part 50 along Z-direction. A supportpart 62 drives the holding part 50 along X-direction. A support part 63drives the holding part 50 along Y-direction.

Moreover, above-mentioned components of the holding part 50 and thedriving part 60 are one example. For example, a method for holding theobjects G by the holding part 50 may be clamping.

At the holding part 50 or the driving part 60, the recognition part 70is installed.

The recognition part 70 includes the edge detection device 1 of thefirst, second and third embodiments. Except for the edge detectiondevice, the recognition part 70 includes a camera or a sensor to measurea location of the objects G (loaded on the loading region 20) along adepth direction and a distance between the holding part 50 and theobjects G. The recognition part 70 may be three-dimensional distanceimage sensor.

The light source 2 of the edge detection device 1 is located at thedriving part 60 of the object holding device 10. Specifically, the lightsource 2 of the edge detection device 1 is located on side surfaces oftwo pillars of the support part 61 (driving the holding part 50 alongZ-direction) at a side of the loading region 20. The light-emittingparts 21˜24 of the light source 2 are located by twos, on side surfacesof two pillars of the support part 61 at the side of the loading region20. Furthermore, the light-emitting parts 21˜24 may be located one byone, on side surfaces of four pillars of the support part 61 at the sideof the loading region 20. The imaging part 3 is located at an arm 52 ofthe holding part 50. Furthermore, the imaging part 3 may be located by abeam between two pillars (among four pillars of the support part 61) ata far side from the loading region 20. The detector 4 is included in thecontroller 80.

If the light-emitting parts 21˜24 are respectively located at fourpillars of the support part 61, edges along Z-direction on a face (atthe light source side) of the objects G (loaded on the loading region20) can be notably detected. Furthermore, if the light-emitting parts21˜24 are located at two side faces of two pillars (at the loadingregion side) of the support part 61 by twos, edges along Y-directionand/or Z-direction on a face (at the light source side) of the objects Gcan be detected.

Furthermore, the light-emitting parts 21˜24 may be located on theholding part 50. In this case, the imaging part 3 is also preferablylocated on the holding part 50. As a result, in proportion to moving ofthe holding part 50, edges at a desired portion of the objects G (loadedon the loading region 20) can be detected.

In above explanation, the number of the light-emitting parts is four.However, the number thereof is not limited to four, and may be at leastthree.

The controller 80 controls driving of the holding part 50 and thedriving part 60. Furthermore, the controller 80 includes the detector 4of the edge detection device 1, and detects edges of the objects G basedon image data imaged by the imaging part 3. A method for detecting edgesis same as that of the first embodiment. The controller 80 recognizesposition of objects based on detected edge information of the objects,and controls driving of the holding part 50 and the driving part 60.

In the object holding device 10 of the fourth embodiment, by equippingthe edge detection device 1, position of the loaded objects G can berecognized accurately.

Furthermore, by recognizing edges of the loaded objects G along a heightdirection, interference or collision of the holding part 50 with theloaded objects G can be prevented.

The object holding device 10 of the fourth embodiment includes adepalletizing device, a palletizing device, a picking device, a cargoholding device and so on.

The Fifth Embodiment

The fifth embodiment is explained by referring to FIGS. 11˜16. Componentof an edge detection device of the fifth embodiment is same as the edgedetection device of the first˜third embodiments (refer to FIG. 1 or FIG.9). In the fifth embodiment, a method for detecting edges is differentfrom the edge detection device of the first˜third embodiment.

Specifically, even if an appendix is positioned on a surface of objects(target to detect edges), a method capable of accurately detecting edgesis explained.

FIGS. 11 and 12 are schematic diagrams showing one example of objects asa target to detect edges. FIG. 11 shows an object G including anappendix on surface thereof. For example, the appendix is a gum tape, aplastic tape, a label, a slip, a transmittal letter, an affixing slip,or a tag. FIG. 12 shows an object G having two objects bound by anappendix I. Here, the appendix I is a binding band, a gum tape, aplastic tape, a curing tape, a polypropylene band, a packing string, ora tape.

Next, a method for detecting edges by using the edge detection device ofthe fifth embodiment is explained in detail.

In the imaging part 3 of the fifth embodiment, in addition to image data31˜34 (not shown in Figs.) imaged while four light-emitting parts 21˜24are lighting differently, image data 35 (not shown in Figs.) imagedwhile all of four light-emitting parts 21˜24 are lighting is acquired.These image data is stored into the storage 3A. Based on total fiveimage data, the detector 4 detects edges of a plurality of loadedobjects. Here, the image data 35 is a color image having informationrepresenting color of the object G, which is used for processingexplained afterward. The color image may be an image of RGB (Red GreenBlue) color system, or an image of another color system such as HSV (HueSaturation Value) color system. Furthermore, the image data 35 isacquired by imaging while all light-emitting parts are lighting.However, under a bright environment where color information of theobject G can be acquired, the number of light-emitting parts eachlighting is not limited.

The detector 4 acquires an edge extraction image 36 (not shown in Figs.)by performing same processing as the edge detection device of thefirst˜third embodiments to the image data 31˜34. However, in the edgeextraction image 36 in the case that the object G includes an appendix,in addition to edges of the object G, edges of the appendix is alsoincluded.

FIG. 13A shows a regular color image acquired by imaging objects, andFIG. 13B shows an edge detection image acquired by the edge detectiondevice of the third embodiment. As shown in arrows of FIG. 13A, at abinding band of the object G and a transmittal letter of the appendix,edges different from those of the object G are confirmed. The detector 4of the fifth embodiment performs processing to remove the edges of theappendix.

Hereinafter, processing to remove edge information of the appendix isexplained in detail.

First, by dividing a color of the image data 35, the detector 4 acquiresa plurality of color-divided image data (not shown in Figs.) from theimage data 35. For example, after the detector 4 generates HSV imageincluding three components (hue, saturation, brightness) from a regularRGB image, the detector 4 divides values of saturation into apredetermined each range. By this processing, the object G and theappendix are divided by saturation. The color-divided image data is animage in which the objects and the appendix are divided. FIG. 14 is oneexample of a plurality of images of which color is divided bysaturation. As shown in FIG. 14, it is understood that the objects andthe appendix are divided by value of saturation. Moreover, the methodfor acquiring color-divided image data by saturation was explained.However, instead of saturation, a hue, a brightness, or a luminance maybe used. Furthermore, value of each component of RBG may be used.

Next, the detector 4 detects an external form of a plurality of objectsphotographed into each of color-divided image data. For example,detection of the external form is performed by detecting a circumscribedquadrangle from respective color-divided image data. FIG. 15A shows aregular color image acquired by imaging objects, and FIG. 15B shows animage acquired by overlapping circumscribed quadrangles of therespective color-divided image data. As shown in FIG. 15B, it isunderstood that external forms of both the object G and the appendix aredetected. Moreover, form to be detected from the color-divided imagedata is not limited to the circumscribed quadrangle. Another polygon, acircle, or an ellipse, may be detected. In processing up to this moment,external forms of the object G and the appendix are detectedrespectively.

Next, the detector 4 decides whether the detected external form belongsto the object G or the appendix. For example, this decision processingis performed as following steps.

An eternal form and a line involved in another external form are decidedas an appendix. For example, they are decided as an external form suchas a label (step 1). E part in FIG. 15B is corresponded. The externalform of which aspect ratio is larger than a predetermined value isdecided as the appendix. For example, it is decided as an external formsuch as binding band (step 2). F part in FIG. 15B is corresponded. Anexternal form not decided as the appendix in steps 1 and 2 is decided asan external form (edge) of the object G (step 3).

Next, the detector 4 b removes edge information decided as the appendix(by above-mentioned steps) from the edge extraction image 36. Thisprocessing is performed, for example, by multiplying a binary image (aninner part of the external form (decided as the appendix) is black, andan outer part thereof is white) with the edge extraction image 36 foreach pixel.

By above-mentioned processing, from the edge extraction image 36, animage 37 (not shown in Figs.) without edge information of the appendixis acquired. If necessary, the detector 4 may perform segmentationprocessing and so on to the image 37. By the segmentation processing, aregion where respective objects are photographed can be determined.

FIG. 16 is a flow chart of processing of edge detection method accordingto the fifth embodiment. First, by the same processing as the thirdembodiment, the edge extraction image 36 is acquired. This edgeextraction image 36 is acquired by same steps as those of flow chart inFIG. 3 (S313).

Next, the detector 4 acquires image data 35 as a color image from thestorage 3A (S1601).

Next, the detector 4 acquires a plurality of color-divided image data bydividing a color of the image data 35 into each range (S1602).

Next, the detector 4 detects an external form photographed into eachimage of the color-divided image data (S1603).

Next, the detector 4 decides whether the external shape (detected fromeach image) belongs to the object G or the appendix (S1604).

Next, the detector 4 generates a binary image in which an inner part ofthe external form (decided to belong to the appendix) is black.Furthermore, by multiplying the binary image with the edge extractionimage 36 for each pixel position, the detector 4 removes edges of theappendix from the edge extraction image 36 (S1605).

Next, if necessary, the detector 4 performs segmentation processing toan image acquired at S1605 (S1606). Hereafter, processing is completed.

By using the edge detection device of the fifth embodiment, withouterroneously detecting edges of the appendix, only edges of the object Gcan be detected accurately.

Furthermore, the edge detection method of the fifth embodiment can beapplied to various objects G including the appendix. Accordingly,application range of the edge detection device can be further enlarged.

Furthermore, above-mentioned processing can be performed by the detector4 only. Accordingly, without increasing component of the device, effectof the invention can be realized with compact component.

Furthermore, by packaging the edge detection device of the fifthembodiment into the object holding device of the fourth embodiment,recognition accuracy of the object by the object holding device can befurther improved.

In above explanation, the edge detection devices according to the first,second, third and fifth embodiments are limited to objects being loaded.However, they are not limited to the objects being loaded. For example,the edge detection devices can be applied to edge-detection of aplurality of objects flatly placed without gaps therebetween.Furthermore, as to a plurality of objects (without gaps therebetween)being conveyed onto a sorter such as a distribution warehouse, the edgedetection devices can be applied to edge-detection of the objects for adividing machine or a sorting machine to divide or sort the objects.

While certain embodiments have been described, these embodiments havebeen presented by way of examples only, and are not intended to limitthe scope of the inventions. Indeed, the novel embodiments describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An edge detection device comprising: a lightsource including at least three light-emitting parts for irradiating aplurality of objects adjacent with a light; an imaging part that imagesa surface of the objects irradiated by each of the light-emitting parts,and generates a plurality of image data of the surface; and a detectorthat detects edges of the surface imaged, based on at least twodifferent combinations of the plurality of image data, wherein thelight-emitting parts are respectively located so as to put a first planetherebetween, and are located on a second plane where the objects areplaced, the first plane includes a line segment connecting the objectswith the imaging part, and is in parallel to a direction of the edges,each of the different combinations includes one image data of thesurface imaged by irradiating from one light-emitting part located atone side of the first plane among the light-emitting parts, and anotherimage data of the surface imaged by irradiating from anotherlight-emitting part located at the other side of the first plane amongthe light-emitting parts, the detector calculates a difference imagebetween the one image data and the another image data in each of thedifferent combinations, and detects the edges by multiplying two pixelvalues at a same pixel position between two difference images of thedifferent combinations.
 2. The edge detection device according to claim1, wherein the light-emitting parts includes a first light source and asecond light source to put the first plane therebetween, the first lightsource and the second light source respectively including at least onelight-emitting part, and the detector detects the edges of the surface,based on at least two different combinations of a first image data ofthe surface imaged by irradiating from the at least one light-emittingpart of the first light source, and a second image data of the surfaceimaged by irradiating from the at least one light-emitting part of thesecond light source.
 3. The edge detection device according to claim 1,wherein, if the light-emitting parts are located on a third planeapproximately in parallel to the second plane, the detector detectsedges of the surface along a direction crossing the second plane.
 4. Theedge detection device according to claim 1, wherein the light-emittingparts are respectively irradiating the objects with a light at differenttimings, and while one light-emitting part is irradiating the objectswith a light, other light-emitting parts are located so as not to enterinto an irradiated region of the one light-emitting part.
 5. The edgedetection device according to claim 1, wherein a wavelength of the lightof the light-emitting parts is larger than or equal to 400 nm, andsmaller than or equal to 2000 nm.
 6. The edge detection device accordingto claim 1, further comprising: a display that displays a detectionresult of the edges of the surface.
 7. The edge detection deviceaccording to claim 1, wherein at least one of the plurality of imagedata is a color image including color information.
 8. A method fordetecting edges in an edge detection device, the edge detection deviceincluding a light source including at least three light-emitting partsfor irradiating a plurality of objects adjacent with a light, an imagingpart that images the objects irradiated by each of the light-emittingparts, and a detector that detects edges of the objects, thelight-emitting parts being respectively located so as to put a firstplane therebetween, and being located on a second plane where theobjects are placed, the first plane including a line segment connectingthe objects with the imaging part, and being in parallel to a directionof the edges; the method comprising: irradiating by each of thelight-emitting parts, a surface of the objects with the light; imagingby the imaging part, the surface irradiated by each of thelight-emitting parts; generating by the imaging part, a plurality ofimage data of the surface; and detecting by the detector, edges of thesurface, based on at least two different combinations of the pluralityof image data, wherein each of the different combinations includes oneimage data of the surface imaged by irradiating from one light-emittingpart located at one side of the first plane among the light-emittingparts, and another image data of the surface imaged by irradiating fromanother light-emitting part located at the other side of the first planeamong the light-emitting parts, wherein the detecting includescalculating a difference image between the one image data and theanother image data in each of the different combinations, and detectingthe edges by multiplying two pixel values at a same pixel positionbetween two difference images of the different combinations.
 9. Anobject holding device comprising: an edge detection device comprising: alight source including at least three light-emitting parts forirradiating a plurality of objects adjacent with a light; an imagingpart that images a surface of the objects irradiated by each of thelight-emitting parts, and generates a plurality of image data of thesurface; and a detector that detects edges of the surface imaged, basedon at least two different combinations of the plurality of image data,wherein the light-emitting parts are respectively located so as to put afirst plane there between, and are located on a second plane where theobjects are placed, the first plane includes a line segment connectingthe objects with the imaging part, and is in parallel to a direction ofthe edges, each of the different combinations includes one image data ofthe surface imaged by irradiating from one light-emitting part locatedat one side of the first plane among the light-emitting parts, andanother image data of the surface imaged by irradiating from anotherlight-emitting part located at the other side of the first plane amongthe light-emitting parts, the detector calculates a difference imagebetween the one image data and the another image data in each of thedifferent combinations, and detects the edges by multiplying two pixelvalues at a same pixel position between two difference images of thedifferent combinations; and at least one of a holding part and a drivingpart.